Colorimetric Nanosensor Based on the Aggregation of AuNP Triggered by Carbon Quantum Dots for Detection of Ag+ Ions

A novel colorimetric nanosensor based on stable aggregation of gold nanoparticle (AuNP) triggered by carbon quantum dots (CDs) has been developed for detection of Ag+ ions in the presence of glutathione (GSH). First, the nanosensor is constructed by assembling carbon quantum dots (CDs) “shell” on the surface of gold nanoparticle (AuNP), resulting in the generation of the stable aggregation of CDs/AuNP. The solution color changes from red to blue. In the absence of target, the addition of GSH into the aggregated CDs/AuNP exhibits the dispersion state corresponding to the color change from blue to red, because GSH can prefer to binding with AuNP comparing with CDs. On the contrary, the aggregated CDs/AuNP has been again observed with the color change from red to blue after the target analyte Ag+ ions are added. Therefore, the new sensing strategy based on “aggregation-dispersion-aggregation” or “blue-red-blue” mode can be established for Ag+ detection. This method can selectively detect Ag+ in a linear range from 100 to 4000 nM with the detection limit of 50 nM. It is successfully applied to determination of Ag+ ions in tap water and lake water. Our study will expand a new sight for application of CDs in sensors, environmental monitoring and preparation of carbon-based nanomaterials.